The present invention relates to a vehicle control unit structure, which includes a pair of circuit boards in each of which conductive layers are adhered on a metal substrate through an insulating layer, and a circuit element is fixed to each conductive layer. More particularly, the invention is directed to a vehicle control unit structure, in which conductive layers are connected to each other through a connecting substrate, and are separated from each other to face each other.
Conventionally, a technique disclosed in Japanese Patent Publication No. 46-13234 is known for an integrated circuit having a pair of metal substrates, wherein conductive layers are adhered to each metal substrate through an insulating layer, a circuit element is fixed to each conductive layer, and the conductive layers are connected through a connecting substrate, and are separated from each other to face each other. A method of manufacturing the integrated circuit disclosed in this prior art comprises the step of anode-oxidizing at least one ma]or surface of an aluminum substrate to form a thin aluminum oxide layer on the substrate surface, the step of selectively bonding and forming a resistive material and a high-conductivity material o the thin aluminum oxide film to form a plurality of circuit elements, the step fixing transistor pellets on lead portions formed by selectively bonding the high-conductivity material, and the step of sealing at least all the circuit elements.
In the integrated circuit formed in this manner, heat radiated from the resistors or transistors is quickly and effectively dissipated to allow formation of an integrated circuit of an output circuit or the like.
The integrated circuit formed in this manner may be employed in a vehicle in view of its compact structure and low cost. However, when the integrated circuit is actually used in a vehicle, the presence of a circuit element which cannot be mounted on the metal substrate poses a problem. In order to arrange the circuit element which cannot be mounted on the metal substrate while connecting it to the integrated circuit, the circuit element must be externally mounted. In this case, even if the integrated circuit is made compact, its merit cannot be sufficiently enjoyed.